Compilare: main.cpp: In function 'void handle(const string&)': main.cpp:21:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp: In function 'void permute(int, std::__cxx11::string)': main.cpp:30:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == (s.length() - 1)) { ~~^~~~~~~~~~~~~~~~~~~ main.cpp:38:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = i; j < s.length(); j++) { ~~^~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:64:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v.size();i++) ~^~~~~~~~~